Department of Psychology and Jyväskylä Centre for Interdisciplinary Brain Research, University of Jyväskylä, Jyväskylä 40014, Finland.
J Neurosci. 2014 Apr 23;34(17):6003-10. doi: 10.1523/JNEUROSCI.4859-13.2014.
Hippocampal local field potentials are characterized by two mutually exclusive states: one characterized by regular θ oscillations (∼4-8 Hz) and the other by irregular sharp-wave ripples. Presenting stimuli during dominant θ oscillations leads to expedited learning, suggesting that θ indexes a state in which encoding is most effective. However, ripple-contingent training also expedites learning, suggesting that any discrete brain state, much like the external context, can affect learning. We trained adult rabbits in trace eyeblink conditioning, a hippocampus-dependent nonspatial task, followed by extinction. Trials were delivered either in the presence or absence of θ or regardless of hippocampal state. Conditioning in the absence of θ led to more animals learning, although learning was slower compared with a yoked control group. Contrary to expectations, conditioning in the presence of θ did not affect learning. However, extinction was expedited both when it was conducted contingent on θ and when it was conducted in a state contrary to that used to trigger trials during conditioning. Strong phase-locking of hippocampal θ-band responses to the conditioned stimulus early on during conditioning predicted good learning. No such connection was observed during extinction. Our results suggest that any consistent hippocampal oscillatory state can potentially be used to regulate learning. However, the effects depend on the specific state and task at hand. Finally, much like the external environment, the ongoing neural state appears to act as a context for learning and memory retrieval.
一种以规则的θ振荡（~4-8 Hz）为特征，另一种以不规则的尖波涟漪为特征。在主导θ振荡期间呈现刺激会加速学习，这表明θ指数编码最有效的状态。然而，与尖波相关的训练也会加速学习，这表明任何离散的大脑状态，就像外部环境一样，可以影响学习。我们在痕迹性眨眼条件反射中训练成年兔子，这是一种依赖海马体的非空间任务，然后进行消退。试验要么在θ的存在下进行，要么在没有θ的情况下进行，要么不考虑海马体的状态。在没有θ的情况下进行条件反射会导致更多的动物学习，尽管与配对对照组相比，学习速度较慢。与预期相反，在θ存在的情况下进行条件反射并不会影响学习。然而，当θ与条件反射相关联或在与触发条件反射试验的状态相反的状态下进行时，消退都会加快。在条件反射早期，海马θ频带反应与条件刺激的强相位锁定可以预测良好的学习。在消退期间没有观察到这种联系。我们的结果表明，任何一致的海马体振荡状态都有可能被用来调节学习。然而，具体效果取决于特定的状态和任务。最后，就像外部环境一样，持续的神经状态似乎可以作为学习和记忆检索的背景。
